While only the physical elements of fighting strength are susceptible of quantitative comparison, failure to take account of mental and moral factors may involve serious error. Nevertheless, in many situations, such factors remain relatively indeterminate until subjected to test. Inferences may be drawn, and deductions made, on a basis of peace-time observation and of historical precedent. In these, racial and national characteristics may figure prominently. History, however, has taught that, in a conflict between modern industrial and military nations, it is unwise to entertain any assumption other than that of moral equality until such time as the conflict has demonstrated the existence of a difference, and the degree thereof, or unless prior experience, observation, and acquaintance unquestionably warrant otherwise. (iv) Information and counter-information measures. Operations of war are tremendously affected by the information which each belligerent possesses of the others. It is therefore of vital importance to weigh the efficiency of the belligerents in the employment of means of obtaining, denying, and utilizing information. There may appropriately be considered present, probable, or possible use or non-use of indirect methods such as: study of press, captured documents, and material; reports from other friendly units; interrogation of prisoners of war, deserters, inhabitants, and escaped or exchanged prisoners; radio direction-finding; efficiency of cryptography; interception of enemy radio, telegraph, telephone, and mail communications; espionage; censorship; propaganda; efficiency of communications systems, ashore and afloat, which include all means of interchange of thought. In this connection it will be recalled that information, however accurate and appropriate, is useless if it cannot be conveyed in time. The direct methods of obtaining information are military operations intended for that purpose, such as observation, reconnaissance, scouting, trailing. Counter-information measures are no less important than those pertaining to collection of information. Such measures include all provisions for secrecy, such as censorship, counter-espionage, cryptography, control of own communications, security of documents, camouflage, and applicable tactical operations. (b) Factors More Directly Applicable to Armed Forces, (i) Vessels, including aircraft. The numbers and characteristics, of the ships and aircraft of the various nations of the world are known with less and less accuracy from the time when war becomes a probability. The information available is given intense and comparative scrutiny, under the specific headings of the factors of the Estimate Form as later enumerated.